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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [Attributor] Failure to propagate alignment through PHI when may have null incoming value"
href="https://bugs.llvm.org/show_bug.cgi?id=44602">44602</a>
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<th>Summary</th>
<td>[Attributor] Failure to propagate alignment through PHI when may have null incoming value
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<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Global Analyses
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>lebedev.ri@gmail.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<p>
<div>
<pre><a href="https://godbolt.org/z/jryz4D">https://godbolt.org/z/jryz4D</a>
define void @square(i1 %c, i32* align 32 %dst) #0 {
br i1 %c, label %truebb, label %falsebb
truebb:
br label %end
falsebb:
br label %end
end:
%ptr = phi i32* [ %dst, %truebb ], [ null, %falsebb ]
store i32 0, i32* %ptr
ret void
}
attributes #0 = { "null-pointer-is-valid"="true" }
Regardless of whether or not null is legal address,
we should annotate that store with `align 32`,
because `%ptr` can either take the value of `i32* align 32 %dst`,
or `null`. Because `null` is *always* aligned - no bits are set.
I might take a stab at this..</pre>
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